I am a member of a search and rescue unit in Southern California . We are
about to start using APRS to track our teams in the field during events. For
several reasons, we have selected TM-D700 radios for our vehicles and TH-D7A
radios for our ground pounding teams (one per team). We will be using UIview
at the command post. After much research on the Internet I am confused on
how to set up field Digi's so that we complement (not hinder) the LA/OC
fixed digi's and network load.
Here is a scenario so you can get a feel of the challenge.
There is a search In the eastern mountains of Orange County, lets say in a
canyon. The command post is in the canyon (RF hole), teams are in other
canyons and high on hills (LOS to a wide area digi). The foot teams do not
digi but the vehicles do. Placement of one or more vehicles might be
strategically selected to digi the canyon units to the command post and into
the public digi system for Internet monitoring by command staff back at an
EOC. If resources are thin, the vehicle(s) will be part of the search and
could be anywhere. One of the goals is to pre-set the radios so that little
if any configuration settings need to be changed in the field. A
transportable digi in a box (KPC-3/radio/battery) can also be used if a
long-term search is anticipated. The multiple canyons (hidden transmitters)
and the high stations make the solution tricky.
The two ways I think it can go are:
1. The D700's digi's have UIFLOOD set to "UIFLOOD WIDE,FIRST" and the
trackers use WIDE3-3 for location beacons. The D700's that could hear each
other would not duplicate packets but would propagate them back to the
command post and potentially into the OC/LA network via the WIDE public
digi's.
Downsides: The D700's mobiles on high hills might pickup traffic in the
OC/LA network and use up hops, especially if they were high on a hill.
2. The D700's digi's have a digi alias of WIDE1-1, no UIFLOOD and the
trackers use "WIDE1-1, WIDE2-2" for location beacons. The first D700 that
heard a location beacon would strip off the WIDE1-1 and digi the WIDE3-3
which would only be picked up by the LA/OC network (if it heard it and there
was no collision). The LA/OC network might hear the WIDE1-1 beacon but it
would do little harm.
Downsides: The command post is less likely to get one-hop beacons as the
one local digi might be out of range of the command post.
The LA/OC network also might not hear an individual
beacon.
Upside: The local digi's ignore LA/OC traffic.
Do you know if the D700 Group Code applies to digipeating? The manual says
that when the UNPROTOCOL (menu 3-E) is set to something starting with other
than AP, like SPCL - the radio ignores any packet that is directed to other
than SPCL. This way choice #1 would ignore the LA/OC traffic and might
become the choice.
Got any other ideas?
Steve